Electric circuit breaker with thermalmagnetic tripping means



g- 15, 1967 K. J. STOKES 3,336,545

ELECTRIC CIRCUIT BREAKER WITH THERMAL-MAGNETIC TRIPPING MEANS Filed Dec 8, 1965 INVEN'IOR. F3 G I 4. KENNETH 570/055 A TTURNEV United States Patent 3,336,545 ELECTRIC CIRCUIT BREAKER WITH THERMAL- MAGNETIC TRIPPING MEANS Kenneth J. Stokes, Wethersfield, Conm, assignor to General Electric Company, a corporation of New York Filed Dec. 8, 1965, Ser. No. 512,300 3 Claims. (Cl. 335-41) ABSCT OF THE DISCLOSURE A manually and automatically operable switch device having a contact arm which operates upon every manual operation of the device, in which the contact arm includes a generally U-shaped portion of magnetic material and a conductor passing between sides of said U-shaped portion whereby this portion acts as an electro-magnetic field piece and attracts an armature upon the occurrence of unusually high currents to cause release of an automatic opening device.

The present invention relates to electric circuit breakers of the type including manually operable operating means for moving the contacts thereof between open and closed circuit positions, combined with automatically operable means for automatically causing opening of the contacts upon the occurrence of predetermined current conditions, and more particularly to electro-magnetic tripping means for such circuit breakers.

In electric circuit breakers of the type referred to, basic design objectives include small size, simplicity of construction and assembly, as well as effectiveness of operation. Such circuit breakers commonly are required to include both thermal and magnetic means for causing automatic opening of the circuit breaker. Thus, in accordance with the prior art, a thermally responsive member such as an elongated bimetallic strip is commonly provided, and also a movable armature member and stationary magnetic field piece for acting on the armature member. These elements, are of course in addition to the mechanical operating means required for operating the contacts. The necessity for providing, assembling, and installing all of these parts establishes certain limitations on the size and cost of the circuit breaker. The elimination of any of such parts, without elimination of the function performed by it, would permit a desirable reduction in size and cost.

Accordingly it is an object of the present invention to provide a manually and automatically operable circuit breaker including magnetically operable means, which does not require as many parts as prior art circuit breakers of thistype.

It is another object of the invention to provide an elec tro-circuit breaker including magnetically operable means for initiating automatic opening which is extremely simple in construction and assembly, and of relatively low cost.

In accordance with the invention, an electric circuit breaker is provided including at least two relatively movable contacts and manually and automatically operable mechanism for operating the contacts between open and closed circuit positions. The operating mechanism also includes a contact arm for operating one of the contacts. An automatic operating mechanism is provided, including a releasable member releasable to cause automatic opening of the contacts, and a magnetically operable armature for causing release of the releasable member. In accordance with the invention, the contact arm of the circuit breaker mechanism is constructed and arranged so as to perform the function of a magnetic field piece as well as that of a contact arm, so as to act on the magnetic armature to cause release of the releasable member upon the occurrence of predetermined current conditions.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevation view of an electric circuit breaker incorporating the invention, a portion of the side wall nearest the observer being broken away to show some of the interior parts;

FIGURE 2 is a side elevation view of a portion of the mechanism of the circuit breaker of FIGURE 1;

FIGURE 3 is an exploded perspective View of a portion of the mechanism of FIGURES 1 and 2, and

FIGURE 4 is a fragmentary sectional view taken generally on the line 4-4 of FIGURE 1.

In FIGURE 1, the invention is shown as incorporated in an electric circuit breaker having a casing including a base portion 10 and a cover portion 11. The casing includes three pole chambers 12, 13', and 14 (see FIGURE 4). Each of the chambers 12, 13 and 14 contains parts similar to those shown in compartment 12 in FIGURE 1, and therefore the parts in this compartment only will be described in detail.

A load terminal 15 is supported on the casing adjacent one end of each of the compartments and is connected by a strap 16 to an elongated heater conductor member 17, the other end of which is connected to the stationary end of an elongated bimetallic strip 18. The conductor 17 and the bimetallic strip 18 are connected together and also connected to a flexible conductor or braid 19 by means of a screw 20. The flexible conductor or braid 19 includes two parallel portions as best shown in FIGURE 3, the other ends of which are connected to an end portion of a movable contact carrying member 21. The contact carrying member 21 is pivotally supported by pivot pin 22 on a generally U-shaped contact arm 23, to be more fully described. A compression spring 25 is interposed between the contact arm 23 and the contact carrier 21. The contact member 21 also supports a movable contact member 21' at its outer end which cooperates with a stationary contact 24' carried by a conductive strap 24 which is connected to an outgoing or line terminal, not shown. The contact arm 23 is rigidly carried by an insulating contactarm 28, see FIGURES 3 and 4, which is pivoted in the base 10 at its ends 28A. The contact cross-arm 28 also carries the con tact arm members 23 of the pole chambers 13 and 14, as shown in FIGURE 4.

The electric circuit path through the pole 12, is therefore as follows: in at load terminal 15, to conductive strap 16, to heater member 1 7, to flexible braid 19, to movable cont-act carrying member 21, to movable contact member 21', to stationary contact member 24, to conductor 24, and finally to the outgoing or line terminal, not shown.

For the purpose of operating the contact arm 23 in unison between open and closed circuit positions, manual and automatic operating means is provided. It will be understood that the use of any particular kind of operating means is not critical to the present invention. For purposes of illustration, however, a particular operating mechanism has been illustrated in part, including a normally latched support or cradle member 30 pivotally supported on a pivot pin 31 fixedly carried by the casing by suitable supporting means, not shown. The cradle member 30 is releasably latched by a pivotally supported latch member 32 mounted on a pivot pin 33. The cradle member 30 has attached thereto a pair of upper toggle links 34, only one shown, by pivot pin 35. A pair of lower toggle links, only one shown, 36 is pivotally connected to the upper toggle links by knee pivot pin 37. The lower toggle links 3 36 are connected to the contact arm 23 of the central pole 13 of the circuit breaker.

For the purpose of operating the toggle links 34, 36, between collapsed and straightened conditions, to thereby rotate the contact arms 23 between open and closed circuit positions, a pair of tension springs 38, only one shown, are provided, which are connected between the toggle knee pin 37 and an anchoring pin 39 carried by a suitable support member, not shown. The pin 39 is arranged to be moved in reciprocating fashion along a path extending generally parallel to the base of the circuit breaker between open and closed circuit positions by a manually operable handle member 40. It will be observed that when the pin 39 is moved in this fashion, the line of action of the springs 38 crosses the pivot pin 35. Thus when in the position shown in FIGURE 1, the springs 38 bias the upper toggle links 34 counterclockwise about the pivot pin 35, whereas when the pin 39 is moved to the left, the line of action of the springs 38 is on the other side of the pin 35, and biases the upper toggle links 34 clockwise about the pivot point 35.

When the parts are in the condition shown in FIGURE 1, release of the cradle member 30 from the latch member 32 permits the cradle member 30 to rotate clockwise about its pivotal support 31, thereby causing the pivot point 35 to move across the line of action of the springs 38, thereby reversing the bias of the springs 38 on the upper toggle links 34 and causing automatic opening of the contact arms. This occurs whether the handle 40 is forcibly held in the on position or not.

The latch member 32 is held in latching position by means of a holding member 41 carried by a common trip bar 42 having a plurality of upwardly extending projections 43 thereon, one for each pole of the circuit breaker. The holding member 41 and latch member 32 are so constructed that a slight clockwise rotation of the trip bar 42 from the latching position shown in FIGURE 1, causes the holding member 41 to move so as to no longer restrain the latch member 32 from rotation in a counterclockwise direction under the bias of the cradle member 30. The member 32 thereupon moves counterclockwise, permitting the cradle member to move clockwise to cause automatic opening as previously described.

The elongated bimetallic strip member 18 carries an actuating screw 18' at the upper end thereof. Upon the occurrence of moderate overload conditions through the circuit breaker, the heater conductor 17 heats the bimetallic strip 13, which thereupon deflects in such a manner as to cause the actuating screw 18' to move to the right as viewed, engaging the projection 43 of the trip bar 42, and rotating the trip bar 42 slightly clockwise to cause tripping.

In accordance with the invention, this thermal tripping action is supplemented by magnetic tripping action by the use of only a single additional element, namely the generally L-shaped magnetic armature member 50, see FIG- URE 3. The armature member 50 includes an armature portion 51, a pivotal support portion 52, and an actuating portion 53. The ends of the pivotal support portion 52 rest in notches -2 in the side walls or barriers of the insulating casing base 10. The armature member 50 is shaped so as to position the armature portion 51 closely adjacent spaced portions 23' of the contact arm 23.

It will be observed that the flexible conductor 19 passes between the side walls of the contact arm 23. The lines of magnetic flux associated with current flowing through the flexible condutcor 19 therefore create magnetic poles at the portions 23. When the current reaches a certain predetermined high value, the armature portion 51 of the armature member 50, is drawn to the portions 23'. When this occurs, the armature member 50 rotates clockwise about its pivotal support portion 52, and the actuating portion 53 engages the projecting portions 43 of the trip bar 42, causing tripping in a manner similar to that described in connection with the bimetallic strip 18.

It will be observed that while the position of the member 23 changes when the parts moved to the open circuit position, this does not interfere with use of the member 23 as a magnetic field piece, since it is never called upon to act as such a magnetic field piece except when the parts are in the closed circuit position. It will be observed, furthermore, that the magnetic armature member 50 operates independently of the bimetallic strip member 18. Accordingly, the air-gap existing between the armature portion 51 and the pole portions 23 is not enlarged or decreased upon deflection of the bimetallic strip member 18.

It will be observed that I have provided an extremely simple and effective electro-magnetic tripping means for an electric circuit breaker, which not only reduces the total number of parts and assembly work involved, but also makes possible a more compactcircuit breaker.

While the invention has been shown in only one embodiment, .it will be readily apparent that many modifications thereof may readily be made. It is therefore intended by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) a support,

(b) at least one pair of relatively movable cont-acts supported on said support,

(c) manually and automatically operable operating mechanism supported on said support and connected to said contacts, said mechanism including a manually operable handle member movable between on and off positions, said mechanism also including a member releasable to cause automatic opening of said contacts and a trip member movable to cause release of said releasable member,

(d) a contact arm supported on said support and movable between closed and open circuit positions, said contact arm comprising a generally U-shaped member of magnetic material,

(e) means connecting said contact arm to at least one of said contacts to move said contact into and out of engagement with the other of said contacts upon movement of said contact arm between said closed and open circuit positions,

(f) means connecting said contact arm to said manually operable member to move said contact arm between said closed and open circuit positions upon movement of said manually operable member between said on and off positions,

(g) an electro-magnetic armature pivotally supported on said support and including a portion positioned adjacent said U-shaped contact arm when said contacts are in closed conditon, and

(h) an electrical conductor extending between the "sides of said U-shaped contact arm and connected electrically in series with said contacts, whereby an excess of current passing through said contacts causes said armature to be attracted to said U-shaped contact arm,

(i) said armature including a portion engaging aid trip member when said armature is attracted to said contact arm to cause release of said releasable member.

2. An electric circuit breaker as set forth in claim 1 wherein said contact arm comprises memberof ferromagnetic sheet-metallic material bent into a generally U- shape having space side portions thereof bent over to provide magnetic pole portions, one of said contacts being pivotally supported on a pivot pin extending between said sides of said U-shaped member.

3. An electric circuit breaker as set forth in claim 1 wherein said support comprises a base of insulating material having a generaly planar bottom Wall, said contact arm being supported on a contact cross-arm extending substantially parallel to said bottom wall and said 5 armature member including an integral pivotal support portion having projecting end portions seated in conforming recesses in said base whereby said armature portion rotates about an axis extending substantially parallel to the axis of rotation of said contact arm.

References Cited UNITED STATES PATENTS 2,659,783 11/1953 Casey 335-23 BERNARD A. GILHEANY, Primary Examiner. H. BROOME, Assistant Examiner. 

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) A SUPPORT, (B) AT LEAST ONE PAIR OF RELATIVELY MOVABLE CONTACTS SUPPORTED ON SAID SUPPORT, (C) MANUALLY AND AUTOMATICALLY OPERATE OPERATING MECHANISM SUPPORTED ON SAID SUPPORT AND CONNECTED TO SAID CONTACTS, SAID MECHANISM INCLUDING A MANUALLY OPERABLE HANDLE MEMBER MOVABLE BETWEEN "ON" AND "OFF" POSITIONS, SAID MECHANISM ALSO INCLUDING A MEMBER RELEASABLE TO CAUSE AUTOMATIC OPENING OF SAID CONTACTS AND A TRIP MEMBER MOVABLE TO CAUSE RELEASE OF SAID RELEASABLE MEMBER, (D) A CONTACT ARM SUPPORTED ON SAID SUPPORT AND MOVABLE BETWEEN CLOSED AND OPEN CIRCUIT POSITIONS, SAID CONTACT ARM COMPRISING A GENERALLY U-SHAPED MEMBER OF MAGNETIC MATERIAL, (E) MEANS CONNECTING SAID CONTACT ARM TO AT LEAST ONE OF SAID CONTACTS TO MOVE SAID CONTACT INTO AND OUT OF ENGAGEMENT WITH THE OTHER OF SAID CONTACTS UPON MOVEMENT OF SAID CONTACTS ARM BETWEEN SAID CLOSED AND OPEN CIRCUIT POSITIONS, (F) MEANS CONNECTING SAID CONTACT ARM TO SAID MANUALLY OPERABLE MEMBER TO MOVE SAID CONTACT ARM BETWEEN SAID CLOSED AND OPEN CIRCUIT POSITIONS UPON MOVEMENT OF SAID MANUALLY OPERABLE MEMBER BETWEEN SAID "ON" AND "OFF" POSITIONS, (G) AN ELECTRO-MAGNETIC ARMATURE PIVOTALLY SUPPORTED ON SAID SUPPORT AND INCLUDING A PORTION POSITIONED ADJACENT SAID U-SHAPED CONTACT ARM WHEN SAID CONTACTS ARE IN CLOSED CONDITION, AND (H) AN ELECTRICAL CONDUCTOR EXTENDING BETWEEN THE SIDES OF SAID U-SHAPED CONTACT ARM AND CONNECTED ELECTRICALLY IN SERIES WITH SAID CONTACTS, WHEREBY AN EXCESS OF CURRENT PASSING THROUGH SAID CONTACTS CAUSES SAID ARMATURE TO BE ATTRACTED TO SAID U-SHAPED CONTACT ARM, (I) SAID ARMATURE INCLUDING A PORTION ENGAGING SAID TRIP MEMBER WHEN SAID ARMATURE IS ATTRACTED TO SAID CONTACT ARM TO CAUSE RELEASE OF SAID RELEASABLE MEMBER. 